Fun MySQL fact of the day: loose scan semi-join
Yesterday, we considered MySQL'sFirstMatch semi-join optimisation, and while it's pretty simple and fairly straight-forward, some queries may just not benefit from it. ... read more
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Fun MySQL fact of the day: table pullouts
As noted yesterday, MySQL 5.6 was released with a large number of optimisations to the subquery engine. In particular, a number of changes were made to optimise for non-scalar, uncorrelated subqueries, allowing them to be run as... you guess it! Joins. ... read moreFun MySQL fact of the day: subquery materialization
Yesterday, we started looking at the semi-join strategies MySQL provides, and today, we're going to continue looking into semi-joins by considering the "materialisation" strategy. ... read moreFun MySQL fact of the day: duplicate weedout
Last week, we started looking at some of MySQL's semi-join optimisations for subqueries. We've already covered materialisiation,FirstMatch, LooseScan, and table pullout optimisations, but there's still one more to clover: the DuplicateWeedout optimisation, and then thistle be the last topic we discuss about about subqueries. ... read more